An ultrasound system has become an important and popular diagnostic tool since it has a wide range of applications. Specifically, due to its non-invasive and non-destructive nature, the ultrasound system has been extensively used in the medical profession. Modern high-performance ultrasound systems and techniques are commonly used to produce two-dimensional or three-dimensional ultrasound images of internal features of target objects (e.g., human organs).
The ultrasound system may provide ultrasound images of various modes including a brightness mode image representing reflection coefficients of ultrasound signals (i.e., ultrasound echo signals) reflected from a target object of a living body with a two-dimensional image, a Doppler mode image representing velocity of a moving target object with spectral Doppler by using a Doppler effect, a color Doppler mode image representing velocity of the moving target object with colors by using the Doppler effect, an elastic image representing mechanical characteristics of tissues before and after applying compression thereto, and the like.
The ultrasound system may transmit the ultrasound signals to the living body and receive the ultrasound echo signals from the living body to form Doppler signals corresponding to a region of interest, which is set on the brightness mode image. The ultrasound system may further form the color Doppler mode image representing the velocity of the moving target object with colors based on the Doppler signals. In particular, the color Doppler image may represent the motion of the target object (e.g., blood flow) with the colors. The color Doppler image may be used to diagnose disease of a blood vessel, a heart and the like. However, it is difficult to represent an accurate motion of the target object (e.g., blood flow) since the respective colors indicated by a motion value is a function of the velocity of the target object, which moves forward in a transmission direction of the ultrasound signals and moves backward in the transmission direction of the ultrasound signals.
Particularly, the ultrasound system may set a sample volume on the brightness mode image, transmit ultrasound signals to the living body based on an ensemble number, and receive ultrasound echo signals from the living to form a Doppler spectrum image corresponding to the sample volume.